There is known a device for making springs from wire, comprising a bed on which a headstock and a tailstock are fixed (SU,A, No. 123138).
The headstock comprises a spindle unit mechanically associated with its rotary primary motion drive, a hollow spindle of which carries a collet mechanically associated with its closing mechanism.
A mandrel serving for spring winding is fitted with its one end into the collet with a nominal clearance equalling two diameters of the wire from which a spring is to be made.
The tailstock comprises a bearing unit, wherein the other end of the mandrel is rigidly secured.
The device also comprises ways arranged along the axis of the spindle, which are in fact grooves provided on the surface of the bed, and a carriage traversable along these ways.
A provision is made for a lead screw, whose one end is associated mechanically with the primary motion drive via the spindle unit and a feed gear-box, while the other end rests upon the bedways. The lead screw serves to facilitate reciprocation of the carriage to the extreme position (spring-winding cycle) and from the extreme position to the initial one (removal of wound springs from the mandrel). there is a nut rigidly secured on the carriage with the lead screw running through its hole.
The device operates as follows.
The mandrel with the pre-wound spring portion is placed in the collet and gripped with the aid of its closing mechanism.
Once the mandrel with the wound spring portion is gripped by the collet, the primary motion drive is cut in to operate the spindle, which imparts rotary motion to the mandrel and the lead screw. While rotating, the lead screw actuates the nut and consequently the carriage, which feeds wire stock onto the mandrel. The rotating mandrel winds wire on itself.
With the carriage in the extreme right-hand position, the spindle comes to a stop, the collet opens, and the wire is no more wound onto the mandrel. At the same time the spindle starts to rotate in the opposite direction and the carriage moves to the extreme left-hand position, the wound spring portion being removed from the mandrel and thrust through the spindle cavity.
With the carriage in the extreme left-hand position, the spindle starts to rotate in the opposite direction, the collet gripping the mandrel with a spring wound on it whereby a new spring portion is wound.
In the known device, the spring-winding cycle alternates with that of removing a wound spring from the mandrel, these two cycles being equal in duration.
Removal of the wound spring portion is an idle run time. Thus the device works almost at 50 percent capacity.
Besides, the screw-nut kinematic pair is worn out severely due to the reciprocating motion of the carriage, whereas the reversible motion greatly affects the primary motion drive, which eventually results in that the kinematic pair and the drive are oftentimes replaced which decreases operating efficiency of the device.